1. Field of the Invention
The present invention relates to a residual toner removal apparatus for removing residual toner adhering to a transferring rotary member for transferring a toner image to a transfer material, and an image forming apparatus equipped with the residual toner removal apparatus.
2. Related Background Art
In conventional image forming apparatuses, there is known an image forming apparatus in which a transfer material (e.g., a sheet) is held between an intermediate transferring member having a toner image formed thereon through primary transferring, and a secondary transferring member capable of being brought into and out of contact with the intermediate transferring member, and secondary transferring of the toner image on the intermediate transferring member to the transfer material is effected (see Japanese Patent Application Laid-Open No. 11-52757). FIG. 9 is a perspective view of a secondary transferring roller pushing mechanism of the image forming apparatus. FIG. 10 is a front view of a main portion of an image transferring apparatus.
A shaft 109a of a secondary transferring roller 109 as a secondary transferring rotary member is rotatably supported at one end of each of arms 137 adapted to rock around rotation shafts 136. The secondary transferring roller 109 rotates integrally with a driven gear 132 coaxial with the shaft 109a. The arms 137 are biased so as to rotate clockwise as seen in the drawing by a spring 138 provided at the other end of one of the arms 137. The secondary transferring roller 109 is pushed against a transfer belt 107 as an intermediate transferring member by the pulling force of the spring 138. The rotation shafts 136 of the arms 137 are shafts common to a shaft 134 of a driving gear 131 or are at least arranged coaxially therewith. At the other end of one of the arms 137, an eccentric cam 139 is arranged so as to be opposed to the arm. The arm 137 is pushed against the cam surface of the eccentric cam 139 by the pulling force of the spring 138.
In this construction, when a flat portion 139a of the eccentric cam 139 is opposed to the arm 137, the arms 137 are pulled by the spring 138 to rotate clockwise, bringing the secondary transferring roller 109 into press contact with the transfer belt 107. When, in this state, the driving gear 131 rotates, the secondary transferring roller 109 is caused to rotate through the driven gear 132. When a transfer material (e.g., a sheet) enters the gap between the rotating secondary transferring roller 109 and the running transfer belt 107, a toner image on the transfer belt 107 is transferred to the transfer material.
When the eccentric cam 139 rotates and its maximum radius portion 139b comes into contact with the arm 137, the arm 137 rotates counterclockwise against the force of the spring 138, separating the secondary transferring roller 109 from the transfer belt 107. The driving gear 131 and the driven gear 132 are constantly in mesh with each other regardless of whether the secondary transferring roller 109 is separated from the transfer belt 107 or is contacted with the transfer belt 107. Residual toner on the transfer belt 107 may adhere to the secondary transferring roller 109. Thus, when it is at a position where it is in contact with the transfer belt 107, the secondary transferring roller 109 is also in contact with a cleaning blade 133, by means of which the residual toner is removed.
In some image forming apparatuses, the residual toner adhering to the transfer belt as the intermediate transferring member is removed by electrostatic cleaning (see Japanese Patent Application Laid-Open No. 2001-337542). FIG. 11 is a schematic front view of a cleaning device 213 of such an image forming apparatus.
The cleaning device 213 forms a cleaning area in a part of a portion where an intermediate transfer belt 207A is in contact with a roller 207B as an opposing roller. The cleaning device 213 is equipped with a first bias roller 224, a first fur brush 223 in contact with the first bias roller 224, a second bias roller 227, a second fur brush 226 in contact with the second bias roller 227, a carrying screw 229, etc. By applying a bias voltage of reverse polarity to the first fur brush 223 and the second fur brush 226, cleaning of the intermediate transfer belt 207A is effected.
In this way, in the conventional image forming apparatuses, it is possible to remove residual toner adhering to the secondary transferring roller and the transfer belt. However, the residual toner adhering to the secondary transferring roller 109 is mechanically removed by the cleaning blade 133. Thus, there is a fear of the secondary transferring roller being damaged. Further, the residual toner is removed by the cleaning blade 133 only when the secondary transferring roller 109 is at the position where it is in contact with the transfer belt 107, resulting in a rather low residual toner removal efficiency.
When the residual toner removal efficiency is low, some residual toner is allowed to adhere to the transfer material, which leads to a deterioration in image quality.